Removable mold core



v United States Patent [111 3,545,718

[72] Inventor KEllllflh A. Shale [56] References Cited m UNITED STATESPATENTS 2 gi No. 22b 1 19 1,347,575 7/1920 Burgay 249/186 1 3,095,6137/1963 Christensen et al. l8/45(MX) [45] Paemed 3 343 801 9/1967 Mungerm1 249/1894 [73] Assignee Contlnental Oil Company pone CRY, OklahomaFOREIGN PATENTS a corporation of Delaware l ,237,243 6/1960 France..1.8/(.undercut Digest) Primary Examiner-J. Howard Flint, Jr.Attorneys-Joseph C. Kotarski, Henry H. Huth, Jerry 8. Peterson, WilliamA. Mikesell, Jr. and Carroll Palmer [54] REMOVABLE MOLD CORE 3 Claims 3Drawing ABSTRACT: An improved segmented mold core for forming [52] [1,5,(I 249/185, hollow curved articles, comprising two reciprocal and only18/45 one articulated segment per radius; the articulated segment is[51] In, (I 1328b 7/30 i retained in position by a friction device. In apreferred em- [50] bodiment, segments are maintained in alinement by atongue- Fleld olSearch 18/45(M),

42(M), (undercut Digest); 249/185, 186

and-groove arrangement.

PATENTEU UEI: 8|97fi 3545718 sum 1 OF 2 INVENTOR.

KENNETH 4. SHALE' BY QMM A TTORNEY PATENTEDUEB 8|97G 3.545 718 I SHEET 2OF 2 I REMOVABLE MOLD CORE This invention relates to a segmented moldcore assembly adapted for injection molding of bent plastic articles,the assembly being characterized by having its outer surface formed fromonly three segments for each curve, two of the segments being moveabletangentially with respect to the curve, and the third being articulatedwith respect to one of the two. According to one aspect, the articulatedsegment is maintained in molding position by a friction device.According to another aspect, the segments are maintained in an alinedposition by a tongue-and-groove arrangement.

It is known in the art that internally-curved objects, such as pipefitting elbows and tees, can be injection molded by use of a segmentedinternal core which is suitable for machine manipulation, as opposed tohand placing of such cores into position. One such internal core deviceis shown by U.S. Pat. 3,095,613, to Christensen et al., issued July 2,1963. It is also known that it is desirableto minimize the number ofsegments which comprise such a mold core assembly, both because of corefabrication costs and because each joint between segments willinevitably cause an imperfection on the surface of the molded object.

It is accordingly an object of the present invention to provide anautomatic segmented mold core assembly, for molding internally-curvedobjects, which exhibit a surface composed of a minimum number ofsegments. It is another object of the invention to provide improvedmeans of alining and maintaining such segments in molding position.

Other aspects, objects, and the several advantages of this inventionwill become apparent upon study of this disclosure, the appended claims,and the drawing, in which:

FIG. 1 comprises a sectional elevation of one embodiment of'thisinvention,

FIG. 2 comprises an oblique view of the core segments of the device ofFIG. 1, and

FIG. 3 comprises an oblique view of the core segments according toanother embodiment of the invention.

Further understanding of the invention will be gained by reference tothe drawing. In FIGS. 1 and 2 are shownan embodiment of the inventionadapted for injection molding of elbow fittings. Although the fittingshown therein is a 90 elbow, it will be obvious to'one skilled in theart that the invention is equally adaptable to other angles, e.g. 30 and45 elbows. FIG. 3 illustrates a variation of the invention suitable formolding tee fittings;

. Referring first to FIGS. 1 and '2, there is shown schematically a molddie which is shaped to contain a cavity conforming to the outer surfaceconfiguration of the fitting 12 which is to be molded. As is known inthe art, molten thermoplastic is supplied to this cavity by a sprue 14.The inner surface of the fitting is shaped by the segmented coreassembly of this invention, which comprise three segments, 16, 18 and20. Segments l6 and Bare each moveable reciprocally along lines normalto the openings in the ends of fitting 12. Such movements are effectedby hydraulic cylinders or equivalent, as is known in the art. Segment 20is moveable out of the cavity reciprocally in the same direction assegment 18, but it is additionally articulated or pivoted on itsoperating rod 22. According to a preferred embodiment of the invention,this segment is pivoted to reciprocable operating rod 22 at two places,points 24 and 26, which are located on extension 28 of rod 22. Extension28 extends through segment 18 in a hole 30, which is of close tolerancefit to extension 28. There is also preferably provided in segment 20 afriction device, such as a bullet or ball 30 which is urged intofrictional engagement with extension 28 by a spring 32. Segment 20 isalso preferably shaped with a rounded comer 34, for a purpose which willbe explained later. in another preferred embodiment of the invention,one of the segments, here 16, is provided with a tongue 36, whichengages corresponding grooves in the other two segments, here 18 and 20.

An operating cycle of the device of FIGS. 1 and 2 will now be described,Assume first that all segments 16, 18 and 20 are in position within themold cavity, in the relationship shown in FIG. 1. Molten plastic isinjected into the cavity, which is of the configuration of elbow 12, byway of sprue M. After a time interval effective to cool the plasticmaterial, which can be aided by coolant passages in the dies and cores,not shown, the core segments are disassembled. This is accomplished byfirst retracting axially the segment 18, while holding segments 16 and20 in position. Next, segment 20 is retracted by its operating rod 22.Linkage 28 is free to drop, by virtue of having retracted segment 18,and segment 20 will thus pivot around points 24 and 26 as it iswithdrawn. Lastly, segment 16 is retracted axially. Die 10 and itsmating die are then opened, and the molded object is discharged. It canreadily be seen that all operations herein described are amenable toautomatic control, as by a time cycle. The mold is readied for anothermolding operation by reversing the die and core disassembly steps justdescribed. Noteworthy in this regard are the rounded end 34 of segment20, which aids in positioning that segment as it is advanced withrespect to segment 16, and friction means 30 and 32, which serves tohold segment 20 in proper relation to linkage 28. Also, tongue 36, incooperation with the corresponding grooves, serves to aline the threesegments in their proper position upon reassembly.

Reference is now made to the device of FIG. 3, which comprises a coreassembly adapted to mold a tee fitting. This assembly and its operationare quite similar to that of FIG. 2, the difference residing in furtherprovision of core assembly segment 38. As before, segments 16 and 18 aremoveable reciprocally along lines normal to the openings in the cavity,as is additional segment 38. Face 40 of segment 38 is shaped to conformto the outer elbow surface of the two segments 16 and 18 when they arein a contiguous position. The operation of this device is like that ofthe device of FIGS. 1 and 2, with the additional step of withdrawingsegment 38 during disassembly of the core, which can be effected eitherprior to, subsequent to, or simultaneously with withdrawal of segments18 and 20.

Although this invention has been described with respect to particularembodiments thereof, it is not to be so limited, as changes andmodifications may be made therein which are within the spirit and scopeof the invention as defined by the appended claims. v

I claim:

l. A segmented mold core assembly adapted to form a curved inner surfacein a molded object, which assembly comprises:

a. two reciprocable inner mold core segments, each of which isreciprocable along a line tangential to a different end of the axis ofsaid curved inner surface;

b. a single extractable additional segmental core part associated withone of said segments and pivotal at least two axes which are disposedalong and perpendicular to said tangential line associated with said oneof said segments;

c. the combination of said two segments and said single core part havingan exterior surface, when abutting during molding, corresponding to saidcurved inner surface; and

d. said single core part being adapted to swing with respect to said oneof said segments so as to exhibit, during withdrawal of said one, across-sectional area with respect to the axis of withdrawal of said one,at least as small as the cross-sectional area of said one.

2. The apparatus of claim 1 further provided with friction means adaptedto tend to maintain the relative position of said single core part tosaid one of said segments.

3. The apparatus of claim 1 wherein at least one of the three piecescomprising said two segments and said core part is provided with atongue alined with its reciprocation axis and adapted to engage acorresponding groove in at least one of the remaining pieces when inabutting position.

Dedication 3,545,718.Kenneth A. Shale, Garrettsville, Ohio. REMOVABLEMOLD CORE. Patent, dated Dec. 8, 1970. Dedication filed Aug. 18, 1971,by the assignee, Uontz'wwntal Oil Uomprmy. Hereby dedicates t0 thePublic the entire remaining term of all claims of said patent.

[Oficial Gazette October 19, 1.971.]

